This thesis explores two important factors that constrain the syntactic parser of the sentence processing mechanism, syntactic storage costs and plausibility information. It uses behavioral methods to explore the characteristics of the two factors and neuroimaging to explore the underlying neurological substrates associated with these aspects of syntactic processing. Experiment 1 behaviorally demonstrated the presence of syntactic storage costs for predictions of verbs, filler-gaps, and subcategorized prepositional phrases. It is argued that the data support the Dependency Locality Theory (Gibson, 2000) supposition of stored predicted heads as well as a theory of syntax that includes empty categories. Experiment 2 demonstrated brain regions associated with storage and integration cost demands in the contrast of subject-object (SO) and object-subject (OS) sentence structures. The results indicate that the inferior parietal cortex is part of a larger network of cortex, including inferior frontal perisylvian areas, that is involved in the processing of SO vs. OS sentences. However, the involvement is not identical to that of the inferior frontal areas and has a distinct hemodynamic character. Experiment 3 explored regions of the brain involved in the resolution of the main verb/reduced relative (MV/RR) ambiguity. Activation was seen in portions of the angular gyrus and the middle temporal gyrus for a contrast in subject noun plausibility, but not structure ambiguity, indicating that the MV interpretation was still considered even in unambiguously relative clause sentence structures. The unexpected results could imply that syntax is not the only factor that determines [theta]-role assignment and ultimately provide evidence about the brain regions involved in(cont.) the process of plausibility information resolution in sentence interpretation.